the importance of exchange 2013 cas in exchange 2013 coexistence | part 2/2 | 3#23

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Page 1 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013 coexistence environment | Part 2/2 Written by Eyal Doron | o365info.com | Copyright © 2012-2015 THE IMPORTANCE OF EXCHANGE 2013 CAS IN EXCHANGE 2013 COEXISTENCE ENVIRONMENT | PART 2/2 | 3#23 In the current article, we will focus on two main subjects: 1. The essence of the relationship that exists between Exchange client and their Exchange CAS server. We will review the different scenario in which different Exchange client addresses the Exchange CAS 2013 asking for a specific information or a specific service.

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The importance of Exchange 2013 CAS in Exchange 2013 coexistence | Part 2/2 | 3#23 http://o365info.com/the-importance-of-exchange-2013-cas-in-exchange-2013-coexistence-environment-part-22/ Reviewing the subject of - Exchange CAS 2013 role in an Exchange 2013 coexistence environment. This is the second article, in a series of two articles. Eyal Doron | o365info.com

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Page 1 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

THE IMPORTANCE OF EXCHANGE 2013 CAS

IN EXCHANGE 2013 COEXISTENCE

ENVIRONMENT | PART 2/2 | 3#23

In the current article, we will focus on two main subjects:

1. The essence of the relationship that exists between Exchange client and their

Exchange CAS server. We will review the different scenario in which different

Exchange client addresses the Exchange CAS 2013 asking for a specific

information or a specific service.

Page 2 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

2. The meaning of the term: “client protocol connectivity flow” in Exchange 2013

coexistence environment. What is the “parts” that construct the client protocol

connectivity flow.

The current article is a continuation of the previous article: The importance of

Exchange 2013 CAS in Exchange 2013 coexistence environment | Part 1/2

Client protocol connectivity flow | The secret

relationship of Exchange client and his

Exchange CAS server

The term “client protocol connectivity flow” appears many times along the current

article series so it’s important that we will understand the meaning of this term.

In simple words, I relate to the term “client protocol connectivity flow” as a

description of the path or the road on Exchange environment that is implemented

when Exchange clients need to access his data or get a specific Exchange service.

Page 3 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

If we want to simplify the term: client protocol connectivity flow we can define two

different “areas”.

In the following diagram, we can see that the first “area” relates to the part in which

different Exchange clients address the Exchange CAS 2013 and ask for “something”

The second “area” is client protocol connectivity flow part which relates to the flow

or the steps that are implemented by the Exchange CAS 2013 “in the background”

or “behind the scenes”. This is that part in which the Exchange 2013 client “forward”

the client request to “other Exchange servers”, that will provide the required

information or a specific service and when this “other Exchange server” reply with

the required information, the Exchange CAS 2013 fetched the information and sent

it to the Exchange client (move again to the first area).

Client protocol connectivity flow | Different

point of views

Page 4 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

In the relationships of client\server who exists between the Exchange clients and

the Exchange CAS server, each of the sides relates to the term “client protocol

connectivity flow” from a different perspective.

1. The Exchange client side

From the Exchange client’s point of view, the term “client protocol connectivity flow”

could be translated into:

How do I find my Exchange CAS server?

Where the Exchange service provides a specific service?

What are the data and the services that I can get from the Exchange CAS server?

2. The Exchange server side

From the Exchange CAS server point of view, the term “client protocol connectivity

flow” is translated into:

What do I need to “do” for getting the required data and “deliver” the data for my

clients?

Do I need to provide a specific service for my client or should I instruct my client

to contact other elements that could provide him the required services?

Page 5 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

As you can see on the diagram, the term client protocol connectivity flow is not just

“one thing” but instead, a “collection” of events and process.

The “yellow rows” (Number 1 and 4), describe the relationships between the

Exchange CAS server and his Exchange mail clients. The Exchange mail client

addresses the Exchange CAS server asking for “information”. The “information”

could be:

The data that is stored in the user mailbox.

Autodiscover information

Exchange web service information such as information about Free\Busy time

with other users

“Redirection” – information about “other elements” that can provide the data or a

specific service.

The “back end” section – the white rows (Number 3 and 2), describe the “back end

operation” that the Exchange CAS server “do for his client”.

The options that are available for the Exchange CAS server are:

1. Provide by himself a specific data or service (the option of “provide by himself,”

is relevant only to Exchange CAS server version 2007 or 2010),

2. Proxy the request to Exchange Mailbox server

3. Proxy the request to “other Exchange CAS servers”

Page 6 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

4. Send a redirection message, which will inform the Exchange client that he needs

to contact “other elements.”

The responsibilities of Exchange CAS server

The Exchange CAS server has a couple of “commitments” to his clients. To be able

to understand better the relationship between Exchange CAS server and Exchange

clients, let’s briefly review the “services” that Exchange CAS server.

Page 7 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

1. Enable Exchange clients to access their mailboxes

Just a quick reminder, in an Exchange environment, the Exchange clients cannot

access their mailbox directly. The only available way for Exchange client to get

accesses his mailbox, is by using the Exchange CAS server as a mediator. Exchange

CAS server except Exchange client’s requests and “fetch” the data from the

Exchange Mailbox server who host the user mailbox “on behalf” of his client.

The Exchange CAS server is responsible for connecting Exchange mail client to their

mailboxes. Most of the time, the Exchange CAS server will “connect” the Exchange

mail client to their mailboxes by proxy the request to Exchange Mailbox server.

Note – the only exception to this rule is a scenario of Exchange 2013/2007

coexistence environment and Exchange 2007 OWA clients. You can read more

information about this scenario in OWA client protocol connectivity flow in

Exchange 2013/2007 coexistence environment | 3/4

In the Exchange 2013 coexistence environment, Exchange 2013 CAS will proxy,

Exchange 2013 client requests to Exchange Mailbox server and Exchange legacy

client’s requests to a legacy Exchange CAS server infrastructure. For example, when

Exchange 2010 address Exchange 2013 CAS in an Exchange 2013 coexistence

Page 8 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

environment, asking to get access to his mailbox, Exchange 2013 CAS will locate

available Exchange 2010 CAS and proxy the request to the Exchange 2010 CAS.

2. Provide\Deliver Autodiscover services.

In an Exchange 2013 coexistence environment, the Exchange 2013 CAS is the

element that is responsible for “delivering” Autodiscover services (information) to

Exchange mail client. I use the term “deliver” because it’s important to emphasize

that the Exchange 2013 CAS is not generating the Autodiscover information by

himself, but instead, “fetch” the information form “other Exchange servers”.

In a scenario in which the Exchange client is Exchange 2007 or Exchange 2013

client, Exchange 2013 CAS will “fetch” the information from the Exchange 2013

Mailbox server.

In a scenario in which the Exchange client is Exchange 20100 clients, Exchange

2013 CAS will “fetch” the information from Exchange 2010 CAS (Exchange 2013

CAS will proxy the request for the Autodiscover information on behalf of the

Exchange 2010 client)

Page 9 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

3. Provide\deliver Exchange web services.

Similar to the concept of Autodiscover services, Exchange 2013 CAS is the element

that is responsible for “delivering” the Exchange web services information to

Exchange clients.

I use again the term: “deliver” because the Exchange CAS 2013 server is not the

element that generates, or actually provides the Exchange web services. Instead the

element that is responsible for providing the Exchange web services infrastructure

is the Exchange 2013 Mailbox server or Exchange legacy CAS server.

In a scenario of Exchange 2013 client, the Exchange clients address the Exchange

CAS 2013 server and ask for the required Exchange web services. Exchange CAS

2013 server will locate the Exchange 2013 Mailbox server and proxy for him the

requests. Exchange 2013 Mailbox server is a real provider of the Exchange web

services.

Page 10 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

In a scenario of Exchange 2007 clients, the Exchange 2007 clients address the

Exchange CAS server with the same version (Exchange 2007 CAS). For example,

Exchange 2007 clients will address the Exchange 2007 CAS when they need

Exchange web services.

The information about the Exchange web services URL for Exchange 2007 is

provided by the Exchange CAS 2013 server in the “Autodiscover phase”.

The information that the Exchange CAS 2013 server provides includes URL

address that “point” to the Exchange 2007 CAS. In an Exchange 2013/2007

coexistence environment, the Exchange 2007 CAS needs to be available for

internal + external Exchange 2007 clients.

In a scenario of Exchange 2010 clients the way that the Exchange web services

are provided depends on the Exchange 2010 client location.

Internal Exchange 2010 client will use the existing Exchange 2010 CAS

infrastructure for getting Exchange web services.

An external Exchange 2010 client will need to get their Exchange web services

from the Public facing Exchange 2013 CAS because, the Exchange 2010 CAS is not

available for the public Exchange client. The Exchange 2010 client will address the

Public facing Exchange 2013 CAS and the Exchange CAS 2013 server will proxy

the Exchange 2010 client request for Exchange web services to the internal

Exchange 2010 CAS.

Page 11 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

The concept of “information” in an Exchange environment

Many times we use the term: ”information” in a sentence such as: Exchange CAS

server provides the required information to his client.

A reasonable question that could appear is: what is this information?

Well, for me, everything that “happened” in the Exchange environment could be

described as: “information”.

For example, when we say that Exchange client access his mailbox, in other words,

we say that the Exchange client gets data\information that is stored in his mailbox.

When we say that Exchange mail client uses the Autodiscover service for creating a

new Outlook mail profile, we can say, in other words, that the Outlook client gets

Page 12 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

the information (Autodiscover information) that includes the required configuration

setting needed for creating an Outlook mail profile.

Other questions regarding the subject of “information” are:

Q1: What is the source of the information?

Q2: Who is the element that delivers the information to the Exchange client?

A1: In an Exchange environment, the only “element” that is authorized to deliver

information to the Exchange client is the Exchange CAS server.

A2: Regarding the question of: What is the source of the information, the answer

depended of the Exchange version and the specific Exchange infrastructure

To be able to better understand meaning of: information provider versus the

information “creator” or “generator” in different Exchange infrastructure, we can

define three major “groups” of Exchange infrastructures:

Exchange CAS 2013 server versus former

Exchange CAS server versions

Exchange CAS 2013 server underwent a significant transformation versus former

Exchange CAS server version such as Exchange 2007 and Exchange 2010.

Page 13 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

To encapsulate the essence of the architecture changes in Exchange 2013, we can

say that the “role” of the Exchange 2013 CAS server was reduced into one purpose:

serve as a “smart router”.

The responsibilities of Exchange 2013 CAS server are:

1. Serve as a “smart router/proxy” – the meaning of this responsibility is to: Enable

Exchange clients to reach their destination (Mailbox data)

2. “Deliver” the information to Exchange client – the meaning of this responsibility

is to: “fetch data” such Exchange web services and Autodiscover from “other

Exchange servers” and deliver the data to his client.

Page 14 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange CAS 2013 server serves as “smart router”, which accepts Exchange mail

client requests and, based on specific charters such as the type of the Exchange

client or the specific protocol decides how to “route” the request to the required

destination.

In former versions of Exchange server, such as: Exchange 2007 and Exchange 2010

the Exchange CAS server role was responsible for:

1. Serve as a “smart router/proxy”

2. “Deliver” information to Exchange client

3. Generate information

4. Render protocol data

Page 15 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

In a former version of Exchange such as: Exchange 2007, Exchange 2010 the role of

the Exchange CAS server includes additional responsibilities.

Besides of being “smart router” the Exchange CAS server was responsible for many

other tasks.

Rendering – the Exchange CAS server was responsible for a task that described

as: “rendering”. The meaning if this term is implementing the task of a protocol

translation. The Exchange mail client uses a specific “language”(protocol) and, the

Exchange CAS server “translate” the Exchange mail client language into other

languages which the Exchange Mailbox server can “understand”

Autodiscover – the element that was responsible for gathering the required

information and generating the Autodiscover information was the Exchange CAS

server.

Exchange web services – the element that was responsible for providing the

Exchange web services was the Exchange CAS server by himself.

Page 16 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

In Exchange 2013, all the “responsibilities” that was mentioned above was “pull out”

from the Exchange 2013 CAS server and was assigned to the Exchange 2013

Mailbox server.

In the Exchange 2013 architecture, the “main load” is lying on the Exchange 2013

Mailbox server shoulders. Exchange 2013 CAS server accepts Exchange 2013 client

requests and, forward (proxy) these requests to the Exchange 2013 Mailbox server.

Exchange 2013 Mailbox server will “do what he needed to do” for example:

Page 17 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

generate Autodiscover information or render protocol information and send back

the “digested information” to the Exchange 2013 CAS server.

In the following comparison table, we can see the deference between the Exchange

2013 CAS server architecture and the “legacy Exchange CAS server versions”

(Exchange 2007, 2010).

The main point of this table is that the only responsibility of Exchange 2013 CAS

server is they serve as a gateway between Exchange mail client and the “rest of the

Exchange infrastructure.” Exchange 2013 CAS server will accept the client request

and forward these requests to “other authority” (Exchange Mailbox server) that will

handle all the operations that relates to the Exchange mail client request.

Versus the “lazy behavior” of Exchange 2013 CAS server who Delegates the

authority to the Exchange 2013 Mailbox server, the legacy Exchange architecture if

the Exchange CAS server was based on a different concept in which the Exchange

CAS server was the “owner” many additional tasks such as generating Autodiscover

answers, rendering protocol data, etc.

Page 18 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange 2013 architecture | Exchange CAS 2013 server

Despite that, this article’s seriously deal with the subject of Exchange 2013

coexistence environment, it’s important to understand in the way that Exchange

2013 CAS operates in a native Exchange 2013 environment that includes only

Exchange 2013 servers and Exchange 2013 clients.

In a “native Exchange 2013 environment” the “division of labor” is very clear:

Exchange 2013 CAS is the component the “delver” information to Exchange

clients and accept Exchange client’s requests that need access to their mailboxes.

Page 19 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange 2013 Mailbox server is the “component” that “hold the date” (user

mailboxes) and generate required data such as: Exchange web services data and

Autodiscover data.

Exchange 2013 Mailbox server is the “component” that is responsible for

rendering protocol data meaning “translating” the Exchange client specific

protocol to the “native” Exchange Mailbox server internal protocol.

Exchange 2013 coexistence environment | Exchange 2010\2007 CAS server

In a “legacy Exchange environment” that’s based on Exchange 2007 or Exchange

2010, the “division of labor” is divided between the Exchange CAS server role and

the Exchange Mailbox server role in the following way:

Exchange 2007/2010 CAS is the component that: “deliver” information to

Exchange clients and accept Exchange client’s requests that need access to their

mailboxes.

Exchange 2007/2010 CAS is the component that: It is responsible for rendering

protocol data meaning – “translating” the Exchange client specific protocol to the

“native” Exchange Mailbox server internal protocol.

Exchange 2007/2010 CAS is the component that is responsible for “generating”

Autodiscover information and Exchange web services information.

Exchange 2013 Mailbox server is the “component” that “hold the date” (user

mailboxes)

Page 20 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange 2013 architecture | Exchange 2013 coexistence environment

Exchange 2013 CAS is the component that: “deliver” information to the Exchange

clients and, accept Exchange client’s requests, which need access to their

mailboxes.

The process of: “rendering protocol data” (“translating” the Exchange client

specific protocol to the “native” Exchange Mailbox server internal protocol) is

implemented by the legacy Exchange CAS server based on the type of the user

mailbox.

For example, in a scenario of Exchange 2010 client, the request will be accepted

by the Exchange 2013 CAS and then, proxy to the Exchange 2010 CAS. The only

exception to this rule is Exchange 2007 OWA client, you can read more

information about this scenario in Exchange 2013/2007 coexistence | Exchange

web service client protocol connectivity flow

“Generating” Autodiscover information and Exchange web services, information –

will be implemented by the legacy Exchange CAS server based on the type of the

user mailbox. For example, in a scenario of Exchange 2010 client, the request will

be accepted by the Exchange 2013 CAS and then proxy to the Exchange 2010

CAS.

Hosting\keep the user’s mailboxes – implemented by the legacy Exchange

Mailbox server based on the type of the user mailbox. For example, an Exchange

2010 mailbox will be hosted on Exchange 2010 Mailbox server.

Page 21 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange 2013 coexistence environment –

Exchange 2007 clients versus Exchange 2010

clients

Regarding the relationships of Exchange CAS 2013 server and his Exchange clients,

we can classify the Exchange clients into two major groups:

1. Exchange 2013 – Exchange clients which their mailbox is hosted on Exchange

2013 Mailbox server.

2. “Other Exchange clients” – in this category, we can include Exchange 2007 and

Exchange 2010 client.

Exchange CAS 2013 server and Exchange 2013 client’s relationships

In a scenario, in which the Exchange CAS server is an Exchange CAS 2013 server and

the Exchange client is also “Exchange 2013 client” (Exchange client that his mailbox

is hosted on Exchange 2013 Mailbox server), the relationships between the “server

and the client” are quite simple to explain.

As mention before, in the Exchange 2013 environment the Exchange CAS 2013

Page 22 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

server serves as a “smart router” that route Exchange clients requites to other

Exchange servers.

All the standard Exchange services are provided by the Exchange 2013 Mailbox

server.

The Exchange 2013 Mailbox server is responsible for generating Autodiscover

infrastructure, render Exchange client’s protocol, provide web services, etc.

Note – in an Exchange 2013 environment, most of the time each of the Exchange

server holds the two roles: Exchange CAS server and Exchange Mailbox server.

In case that the specific Exchange CAS 2013 server who gets the request is also the

Exchange Mailbox server who host the specific user mailbox, the request will be

proxied to the Exchange Mailbox server on the same server.

In case that the Exchange client mailbox is hosted on another Exchange Mailbox

server, the Exchange CAS 2013 server will address (proxy the client request) the

specific Exchange Mailbox server and “fetch” the data for his client.

Page 23 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange 2013 coexistence environment

serving Exchange 2007 & Exchange 2010

clients

The second part of this article seriously, include a very detailed description of the

client protocol connectivity flow in Exchange 2013/2010 coexistence environment

and Exchange 2013/2007 coexistence environment, but, before we will get into the

specific details, let’s quickly review major difference between Exchange 2007 and

Exchange 2010 client protocol connectivity flow.

Page 24 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

Exchange CAS 2013 server and Exchange 2013 client’s relationships

The standard way that Exchange CAS 2013 server use for serving legacy Exchange

clients in an Exchange 2013 coexistence environment is by

1. Proxy the Exchange legacy client request to “legacy Exchange infrastructure”

2. Getting the required data\information

Page 25 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

3. Delivering the data\information to the legacy Exchange clients

Note – there are to 2 exceptions to the “default proxy behavior”:

1. Exchange 2007 webmail client and, OWA mail client in a scenario of regional

namespace and multiple Public facing Exchange site.

You can read more information about this scenario in the article: OWA client

protocol connectivity flow in Exchange 2013/2007 coexistence environment | 3/4

2. Exchange 2007 Autodiscover client – when Exchange 2007 client asks for

Autodiscover information, the Exchange CAS server doesn’t proxy the request to

Exchange 2007 CAS but instead proxy the request to Exchange 2013 Mailbox

server.

You can read more information about these scenarios in the

article: Autodiscover and Outlook client protocol connectivity flow in Exchange

2013/2007 coexistence environment | 2/4

The following tables include just a brief description of the “logic” that Exchange CAS

2013 server use in an Exchange 2013 coexistence environment.

1. Providing access to the mailbox

Page 26 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

On the Exchange 2013 coexistence environment, Exchange CAS 2013 server-client

protocol connectivity flow is based most of the time on the “Proxy” process.

Exchange legacy client such as Exchange 2007/2010 that needs access to their

mailbox content will address the Exchange CAS 2013, Exchange CAS 2013 “find

Outlook” what is the Exchange client version and based on this information, proxy

the Exchange client request to the “suitable” legacy Exchange CAS server.

The exception to the proxy process relates to Exchange 2007 OWA clients. In this

scenario Exchange CAS 2013 will not Proxy the Exchange 2007 client request to the

Exchange 2007 CAS but instead, send a redirection command to the Exchange 2007

browser that includes a “referral” to the Exchange 2007 CAS.

2. Providing Autodiscover services to legacy Exchange clients

From the Exchange legacy client point of view, the Exchange CAS 2013 server is the

“source” for Autodiscover information. As mentioned, the Exchange CAS 2013

doesn’t really “generate” the Autodiscover information, but instead, “fetch” the

Autodiscover information from “other Exchange servers.”

Page 27 of 28 | Part 03#23 | The importance of Exchange 2013 CAS in Exchange 2013

coexistence environment | Part 2/2

Written by Eyal Doron | o365info.com | Copyright © 2012-2015

In a scenario on Exchange 2010 clients, Exchange CAS 2013 gets the Autodiscover

information from Exchange 2010 CAS.

In a scenario on Exchange 2007 clients, Exchange CAS 2013 gets the Autodiscover

information form the Exchange 2013 mailbox.

3. Providing Exchange web services to legacy Exchange clients

In the Exchange 2013 coexistence environment, the process of providing Exchange

web services to legacy Exchange clients is a little confusing because the Exchange

web services “roles” implement differently based on the Exchange legacy client

version and based on the Exchange legacy client location.

Internal Exchange 2010 client – The Exchange CAS 2013, is not responsible or

involved in the process of “providing Exchange web services”. The Internal

Exchange 2010 client will directly address the Exchange 2010 CAS when he needs

Exchange web services.

External Exchange 2010 client – in a scenario of “public” or external Exchange 2010

client, because the Exchange 2010 CAS is not “exposed” to the public client, the

element that provides the Exchange web services is the Public facing Exchange

2013.

Regarding Exchange 2007 client – The Exchange CAS 2013, is not responsible or

involved in the process of “providing Exchange web services”. Exchange 2007 client

will directly address the Exchange 2007 CAS when he need Exchange web services.